1. PHENIX local polarimeter @ RUN9 2009/03/30 @ RHIC meeting Manabu Togawa for the PHENIX 1

2. Leading neutron asymmetry from polarized pp collision Discovered at ZDC kinematics, ±2.8 mrad, in RHIC RUN2. – -10% level in forward kinematics – Consistent with zero in backward 2 Interaction LR definition RUN 2 Asymmetry for neutron ID sample Phys. Lett. B650 : 325-330 (2007)

3. 150 unit:mm 100 Hadron shower 5 PHENIX Setup 3 ZDC (Zero Degree Calorimeter) 10*10cm  ±2.8 mrad 3 modules 150X 0 5.1λ I SMD 1 ZDC SMD (Shower Max Detector) Neutron position can be decided by centroid method. Dx magnet Slat : 7 for x-position 8 for y-position

4. Data set for PHENIX local pol. DAQ mode (offline) Good neutron ID (taking with BBC trigger) Can see phi-dependent  trigger is DAQ band limit (8-10 kHz as maximum)  need time to analysis Scaler mode Many statistics without DAQ band width Get result rapidly  can be high BG  need to start PHENIX DAQ so far (for clock sync.) 4 Detector (ZDC,SMD) FEMDAQ LL1 scaler (FPGA) Start (clock sync.) ADC, TDCCharge SMD : hit map according to TDC hit Until RUN8, we have done LP with DAQ mode. From RUN9, scaler mode is implimented. Accumulating data in each 5 mins. (to DB) * SMD is standby mode except for collision due to the high BG before collimation

5. DAQ mode Phi-dependent asymmetry @ RUN9 5 From first transverse collision at PHENIX, Fill#10228 (2/25) BBCLL1&(ZDCN|S) ~20 M evts By square root formula Blue forward Blue backward Yellow forward Yellow backward

6. Local pol. scaler Threshold for making pattern – 20 MIP equivalent – High threshold is expected to select neutron New! SMD scintillators for x (7 scnti.) LEFTRIGHT Bottom TOP SMD scintillators for y (8 scinti.) Hit patterns are sent by fibers Make hit pattern by TDC in FEM (with high threshold) ZDC LL1 Make scaler in ZDC LL1 board 4 patterns ×2 (N or S) × 120 channels, 20 bits in each! Local pol. scaler is developing by : Cheng-Yi Chi, Ed Desmond, Yuji Goto, John Haggerty, John Lajoie and Manabu Togawa 6

7. Scaler counts (Fill#10454) - 5 mins data (2009/03/29 15:50-55) - Small BG can be confirmed by unfilled bunch 7 Blue : unfilled + yellow : filled Blue : filled + yellow : unfilled Background not related to collision is very low, 10 -3 level for beam gas.

8. Fill#10371 (transverse pol.) 5 mins data RED : yell pol. ↑ BLUE : yell pol. ↓RED : blue pol. ↑ BLUE : blue pol. ↓

9. Systematic study by unpol. beam Unpolarized beam was delivered as Fill#10372 – Cross check for all polarimeters. – Asymmetries in DAQ mode (phi-dependent asymmetry) and scaler mode were consistent with zero. 9

10. DAQ mode : Fill#10372 (unpol.) 10 Blue forward Blue backward Yellow forward Yellow backward

11. Scaler mode : Fill#10372 (unpol.) RED : yell pol. ↑ BLUE : yell pol. ↓RED : blue pol. ↑ BLUE : blue pol. ↓

12. Time dependent @ transverse data From data, polarization is same bunch-by-bunch Fit by following parameters with spin pattern – Blue asymmetry – Yellow asymmetry – Detector asymmetry In this case, – Blue backward asymmetry – Yellow forward asymmetry – Detector asym. in SOUTH ZDC 12 Cross# Measured @ SOUTH RED : yell pol. ↑ BLUE : yell pol. ↓

13. Fill#10288 Extract from SOUTH measurement – Yellow forward asym. – Blue backward asym. – Detector asymmetry in SOUTH 2/25 3:00-7:00 13

14. Fill#10325 Extract from SOUTH measurement – Yellow forward asym. – Blue backward asym. – Detector asymmetry in SOUTH 3/10 0:00-11:00 We have small asymmetry in first 3-4 hours. – High BG from collision related? – Collision angle has been changing? – Situation was changed fill by fill. – For asymmetry value, we took flat region. 14

15. pC vs PHENIX Loc. Pol. Polarization (%), not normalized (!) vs fill Raw asymmetry (%) Online Polarization (%), not normalized (!) vs fill Ratio  2/NDF=21/10  2/NDF=14/9 Fill-by-fill systematics From Sasha’s slide

16. To longitudinal run First beam with rotator on was delivered as fill#10382. 16

17. phi asymmetry (Fill#10382) Value@transverse for BLUE : 0.072±0.004 BLUE forward BLUE backward Yellow forward Yellow backward Value@transverse for YELLOW : 0.079±0.005 17

18. Scaler (Fill#10382) 18 RED : yell pol. ↑ BLUE : yell pol. ↓RED : blue pol. ↑ BLUE : blue pol. ↓

19. First rotator ON : Fill#10382 Raw asym./CNI pol.BLUEYELLOW @ Transverse0.072±0.0040.079±0.005 @ Rotator ON0.011±0.0020.005±0.002 Transverse component15±3 %6±3 % From phi fit (only amplitude) From the scaler Raw asym./CNI pol.BLUEYELLOW @ Transverse0.03380.0379 @ Rotator ON : LR0.00150.0004 @ Rotator ON : UD0.0039 (11.5%)-0.0020 Transverse component12.4 %5.4 % 19 Offline and scaler asymmetries are consistent  Switch to physics data taking at PHENIX

20. Rotator tune at Fill#10399 Rotator feed back during fill : Successfully 20 Rotator current was changed

21. Summary PHENIX LP work is successful. – Scaler mode works well, consistent with offline analysis. Asymmetry is not correct, typically smaller, in the begging of fill due to – High backgroud collision related? – Beam orbit or collision angles are changed? (also appears in detector asymmetry) – First longitudinal data looks transverse component is remained at BLUE beam (radial direction) Feed back is successful during fill. Now it is back to original one due to blue pol. life time. 21

22. Decrease during blue pol.? Fill#10439 22 Increase BG after CNI measurement

23. Detector asymmetry has been changed during fill 23 Increase BG after CNI measurement

24. backup 24

25. Event structure study using pythia input. @ 200 GeV pid 1Gamma10K0 long 2Positron11K+ 3Electron12K- 5Mu+13Neutron 6Mu-14Proton 8Pi+15Antiproton 9Pi-25Antineutron Black : sum Green : gamma Blue : neutron Red : proton n p  ZDC threshold is ~5GeV 25

26. Detector asymmetry 26  Raw asymmetry Blue forward Blue backward Yellow forward Yellow backward Luminosity asymmetry ~ 0.5-1.5% Detector asymmetries are up to 50%, but it is cancelled according to backward asymmetry.

27. ZDC energy distribution with high threshold cut for SMD (in ZDCN|S sample @ RUN5 data) SMD threshold corresponds to 20 MIP – With high SMD cut can be help to select neutron sample. BG1 : photon will stop at 1 st module; not hit SMD. BG2 : proton event is only distributed low energy region. 27 NORTH SOUTH Bottom cut Top cut Left cutRight cut Bottom cut Top cut Left cutRight cut Measured energy in ZDC (GeV) 70 GeV

28. Raw asymmetry for Fill#10228 28 Crossing# (N L -N R )/(N L +N R ) (N B -N T )/(N B +N T ) Measured @ SOUTH LRMeasured @ NORTH LR Measured @ SOUTH TBMeasured @ NORTH TB